Unloader for compressors or the like



June 2, 1942. B. w. MANTLE 2,284,980

I UNLOADER FOR COMPRESSORS OR THE LIKE Filed Dec. 11, 1940 [Jill INVENTOR:

BY fizz/r Ward/514M276 '54 56 6" ATTORNEY Patented June 2, 1942 UNIDADEB FOB GOIIPBESSOBS OR THE LIKE The American Burr Ward Mantle, Plttsiord, N.

Brake Shoe Y., asslgnor to and Foundry Company, a corporation of Delaware Application December 11, 1946, Serial No. 369,556

(flaims. (Cl. 336-24) This invention relates to improvements in unloaders for compressors or the like, and has for a principal object the provision of an unloader which, when a compressor is iirst started up, permits the air pumped thereby to escape to the atmosphere until the speed of the compressor increases to the point where it is pumping air at a definite predetermined volume rate.

Another object of the invention is the provision of an unloader including a valve between the interior of its body and the atmosphere, said valve being normally open and adapted to close when the volume rate of the air or gas pumped by the compressor with which said unloader is associated reaches a predetermined value.

A further object of the invention is the provision of an unloader for compressors, in which a valve between the interior of the unloader and the outside air is balanced by the urge of spring means acting oppositely on each side of said valve, one ,01 said spring means being adjusted to slightly overcome the urge of the other of said spring means, so that said valve opens when the compressor stops, and its high side is in communication with the outside air.

Yet another object of the invention is the provision, in an unloader, of a combined valve and piston around which air may pass at a predetermined volume rate without aflecting the balance of said valve, but when air at a volume rate greater than said predetermined volume rate attempts to pass around said piston, the latter is moved onto its seat, and thereby air is prevented from passing by said piston and seeks its normal channel.

Other objects and advantages of the invention will be apparent to those skilled in the art.

Referring now to the drawing- Figure 1 is a diagrammatic representation of an air compressor outflt employing one of the new and improved volume unloaders between the compressor and the air storage tank;

Figure 2 is a cross sectional elevation of one embodiment of the invention, shown by way of example, as seen along the lines 22 of Figure 4;

Figure 3 is a cross sectional elevation, taken in a plane at 90 with respect to Figure 2, for example along the lines 3-3 of Figure 4;

Figure 4 is a view of the device as shown in Figure 2, as seen from the bottom; and

Figure 5 is a cross section taken along the lines 5-5 of Figure 3.

Referring first to Figure l, the air compressor 26 is connected by means of a belt 2| to a motor 22. The motor and the compressor may be mounted on a common base 23; the intake 24 of the compressor may have secured thereto an air strainer and muilier 35.

A discharge pipe 26, leading from the compressor to an air storage tank 21, may be provided with the usual safety valve 28 and a pressure gauge 23. The pipe 33 maybe provided for leading the compressed air to apoint or points where it is to be used; and the pipe 3| may serve as a blow-oi!" pipe. I

Interposed in the pipe 26 between the compressor and the tank is the usual check valve 32, and a T 34, in which is mounted my new and improved volume unloader 33.

The volume unloader generally designated by the numeral 33, referring now to Figures 2 and 3,

A portion 46 between the main body 35 and the portion of reduced diameter 35 is threaded to engage the lower end of a cap 4|. The lower end 42 of the body 35 is of reduced diameter forming a shoulder 43. The portion 42 is threaded. An annular groove 44 is formed in the lower face of the body 35, preferably in concentric rela-' tion to the bore 36, and an annular ring of suitable seating material is provided for a valve to seat against, as will presently be described.

A tubular member 46 has threads formed on the outside thereof to match the threads of a fitting such, for example, as the T 34. A tubular extension 41 of the tubular member 46 is internally threaded to match the threads 42 on the body.

The interior bore 43 of the member 46 is preferably concentric with the bore 36, and an inwardly extending annulus 49 formed integral with the tubular member 46 forms a shoulder at the bottom of the bore 48 and leaves an opening 56 in the bottom of the tubular portion 46 through which a fluid medium may pass.

A bridge member 5| positioned within the bore 43 bottoms against the annular shoulder 49 and has an upstanding boss 52 which is embraced by the lower end of a spring 53. The lower end of the spring 53 abuts the bridge portion 5|, and the upper end contacts a valve disc 54.

The valve disc 54 has an upstanding annular projection 55 adapted to seat against the annular sealing ring 45. The valve disc 54 has a plu rality of radial arms 56 which engage the walls end of rod 51 contacts the disc 54. A

A spring 59 is positioned within the bore 3 above the disc 58. The lower end of this spring bears on the disc 58, and the upper end bears against a washer 60 which is mounted in the bore 36 prior to the insertion of the spring 59. A threaded plug 6| is provided for adjusting the spring 59 with respect to the spring 53 so that a desired balance between the urges of the springs may be obtained.

The body 35 has cross-holes 62 which lead from the outside air and communicate with the interior of the bore 36 at a point between the disc 58 and the valve 54.

Operation When the compressor-is at rest, the valve assumes its normal position, the position shown in Figure 2. It can be seen that the cross-holes 62 communicate with the bore 36, and the bore 36 communicates with the bore 48, so that air passing into the unloader via the opening 50 is free to pass out to the atmosphere. Therefore, when the compressor is started up, air from the discharge of the compressor passes via the pipe 26 into the T 34 and via the opening, the bore 48, it passes around the edges of the valve disc 54 and then upwardly into the bore 36 and out to the atmosphere via the cross-holes 62. As soon as the compressor has attained its normal speed, the volume rate of the air discharged from the compressor reaches its normal and predetermined rate.

The unloader is so proportioned that just prior to the time that the maximum volume rate of the compressor is attained, the valve disc 54 is urged upwardly against its seat 45 and thereby the egress of air to the atmosphere via the bore 36 and the cross-hole 62 ceases and air is then delivered via the check valve 32 to the tank 21. At this point the motor is running at approximately 50 to 75 r. p. m. above the speed at which the starting winding has cut out and has thereby been conditioned for taking the full load of the compressor or pump which it drives.

After the compressor stops operating, the pressur in the pipe 26 reduces due to leakage via the seat of the discharge valve of the compressor, etc., to a point where the force of the spring 59 in the unloader unseats the valve 54 and again places the interior of the valve in communication with the atmosphere via the cross-holes 62.

The adjustment afforded by the threaded plug 6| permits the device to be adjusted for any given volume rate of air within certain limits so that on size of volume unloader may be set to take care of a number of operating conditions.

Air may pass freely around the valve 54 and out to the atmosphere until the compressor is pumping air at a predetermined volume rate, whereupon the valve 54 is urged against its seat and from then on pressure within the pipe 26 and the fitting 34 maintains this valve on its seat until the pressure is reduced to a point where the urge of the spring 59 is able to again force the valve ofl. its seat.

Although the seat 45 may be made of any material desired, it may preferably be made of a material which has characteristics different from the characteristics of the annular portion 55. In the example herein shown and described, the seat 45 is formed of a rubber like or'resilient material.

My improved unloading device can also be used in connection with air compressor outfits which supply air directly to its point of use without passing the same through either a check valve or a storage tank, in which event the pressure in the pipe'2Ii would fail as soon as the compressor stopped operating.

However, in cases where a check valve and a tank are employed as illustrated in Figure l, the pressure of the air in the discharge line 26 will, depending upon the seat of the discharge valve or valves in the compressor, require a greater or lesser time to drop to a point where the spring 59 can force the valve 54 open.'

For the ordinary compressor installation it has been found that the air escapes sufliciently via the discharge valve seat to permit the valve 54 to open before the compressor starts oper-. ating again.

In case the electric power should fail on the compressor for a few minutes and come back on again before the pressur in the pipe 26 is reduced sufllciently to allow the valve 54 to open, the motor would have to start against the pressure remaining in the discharge line 26. Therefore, an auxiliary means may be provided for quickly releasing the pressure in the pipe 26.

An example of such a device would be a magnetic relief valve associated with the motor line. This valve would open as soon as the power fails and allow the air to escape from the pipe 26.

As soon as the motor started up again the magnetic relief valve would close and would therefore not interfere with the normal operation of the unloader or the operation of the system. This relief valve is indicated diagrammatically in Figure 1 by dotted lines and the number l9.

In describing the unloader above, the closing of the valve is described as occurring when the air passing around the valve 54 attains a predetermined volume rate.

In other words, when the compressor first starts up the volume of air pumped will flow around the valve 54 via the spaces between the radial arms 56.

As the speed of the motor increases the volume rate of the compressor increases to the point where the volume of air can no longer escape around the valve 54 with the result that the valve 54 is pushed on to the seat 45.

The hole or holes 62 may be threaded and may have fittings secured thereto in fluid tight relation for connection to a closed circuit, in cases where the unloader is used for unloading a compressor in a refrigerating system.

Although a simple embodiment of the invention is herein shown and described by way of example in connection with the use of a compressed air system, I do not wish to be limited to the use of compressed air only in connection with my new and improved unloader as it is obvious that it may be used in connection with other fluid mediums, such as gases and liquids. Therefore, the term fluid" or fluid medium appearing in the claims may be taken to mean any fluid medium whether it be air, gas, refrigerants or liquids.

It is obvious that many changes may be made in the arrangement shown without departing from the spirit of the invention as set forth in the following claims.

What is claimed is:

1. In an unloader for compressors, a body having a cylindrical bore formed therein, a second cylindrical bore formed in said body and'communicating with said first cylindrical bore, said second bore being larger in diameter than said first bore, thereby leaving an annular shoulder therebetween, a valve seat mounted in said shoulder, a piston in said first bore, a piston in said second bore, means connecting .said pistons, said second-mentioned piston having open sectors formed adjacent to its periphery and carrying an annular seating face adapted to seat on said valve seat, a cross passage in said body communicating with the atmosphere and with said first bore between said pistons, spring means urging said pistons in one direction, a second spring means urging said pistons in the opposite direction, the balance between the urges of said spring means being such that said second bore is normally in communication with said crosspassage via said first bore, and means to connect said body with its second bore in communication with the discharge of said compressor.

2. In an unloader for compressors, a body having a cylindrical bore formed therein, a second cylindrical bore formed in said body and communicating with said first cylindrical bore, said second cylindrical bore being larger in diameter than said first bore, thereby leaving an annular shoulder therebetween, an annular groove formed in said shoulder, an annular valve seat carried in said groove, a piston in said first bore, a piston in said second bore, a rod connecting said pistons in spaced relation to each other, said second mentioned piston having open sectors adjacent to its periphery and carrying an annular seating face adapted to cooperate with said annular valve seat, a cross-passage formed in said body communicating with the atmosphere and with said first bore between said pistons, spring means urging said pistons in one direction longitudinally, a second spring means urging said pistons in the opposite direction, the urges of said spring means being such that said second piston is normally held out of contact with said valve seat, and means to connect said body with said second bore in communication with the discharge of said compressor.

3. In an unloader for compressors, a body having a cylindrical bore formed therein, a second cylindrical bore formed in said body and communicating with said first cylindrical bore, said second cylindrical bore being larger in diameter than said first bore thereby leaving an annular shoulder therebetween, an annular groove formed in said shoulder, an annular valve seat carriedin said groove, said seat being formed of material diflerent in character from the material of which said body is formed, a piston in said first bore, a disc-like body in said second bore, said disc-like body being smaller in diameter than said second a bore and having radial extensions contacting the wall of said second bore, means connecting said piston and said disc-like members together in spaced relation, an annular contact surface on said disc-like member adapted to seat on said annular valve seat, a passage in said body communicating with the atmosphere and with said first bore between said piston and said disc-like member, spring means urging said disc-like member toward said seat, a second spring means urging said disc-like member away from said seat, the urge of said second spring means being greater than the urge of said first spring means, and means to connect said body with said second bore in communication with the discharge of said compressor.

4. In an air supply system, a conduit leading from the discharge of said compressor to a device utilizing said air, a hollow body in said conduit between said compressor and said device having a free passage formed therein communicating with the interior of said conduit and the atmosphere, a valve seat in said body, a valve in said body for isolating said interior from the atmosphere, a piston in said body carrying said valve, by-pass passages formed in said piston for allowing air to' flow freely from the interior to said free passage when said valve is open, and means balancing said valve to a normally open position, said last means being adapted to be overcome when the reaction on said piston of air passing through said body to the atmosphere when the compressor starts operating attains a predetermined volume rate.

5. In a system for supplying a fluid medium under pressure to a point of use, a compressor,

a conduit for leading the discharge of said oompressor to said point of use, and unloading means in said conduit, including a hollow body serially connected in said conduit, a bore in said body communicating with the hollow interior thereof, a piston in said bore, a second bore smaller in diameter than said first bore and communicating with the latter, a valve seat between said bores, valve means on said piston adapted to engage said seat, a passage formed in said body communicating with said second bore and the atmosphere, apiston in said second cylinder above said passage, means formed on said first piston for normally permitting air to pass thereby, spring means urging said first piston towards said second bore, other spring means urging said second piston towards said first bore, said last spring means overbalancing said first spring means and thereby holding said valve means apart from said seat, said valve means being adapted to be urged into contact with said seat when the rush of the discharge of said fiuid medium past said first piston attains a predetermined volume rate.

BURR WARD MANTLE. 

